OJ Practice 44--t5 Longest palindormic Substring

The longest palindrome substring of the string.

Ideas

1. Start from both sides to the middle

2. From the middle start to the two sides development

3. From the middle of the variant, more complex, see http://articles.leetcode.com/2011/11/longest-palindromic-substring-part-ii.html

"Other code1-Ideas 2"

 stringLongestpalindrome (strings) {intn=s.size (); if(n==0)return ""; stringRE=S.SUBSTR (0,1);  for(intI=0; i<n; i++){            stringp1=Testpalindrome (s,i,i); if(P1.size () >re.size ()) Re=P1; stringP2=testpalindrome (s,i,i+1); if(P2.size () >re.size ()) Re=P2; }        returnre; }    stringTestpalindrome (stringSintC1,intC2) {        intL=C1; intR=C2; intn=s.size ();  while(l>=0&&r<=n-1&&s[l]==S[r]) {L--; R++; }        returnS.SUBSTR (L +1, r-l-1); }

"Result 1"

Time is O (n^2), 100+ms, ranked back.

"Other code2-Ideas 3"

//Transform S into T.//for example, S = "ABBA", T = "^ #a #b#b#a#$".//^ and $ signs is sentinels appended to the end to avoid bounds checkingstringPreprocess (strings) {intn =s.length (); if(n = =0)return "^$"; stringRET ="^";  for(inti =0; I < n; i++) ret+="#"+ S.SUBSTR (i,1); RET+="#$"; returnret;} stringLongestpalindrome (strings) {stringT =preprocess (s); intn =t.length (); int*p =New int[n]; intC =0, R =0;  for(inti =1; I < n1; i++) {    intI_mirror =2*c-i;//equals to I ' = C-(i-c)P[i]= (R > i)? Min (r-i, P[i_mirror]):0; //attempt to expand palindrome centered at I     while(T[i +1+ P[i]] = = T[i-1-P[i]]) P[i]++; //If palindrome centered at I expand past R,//Adjust center based on expanded palindrome.    if(i + p[i] >R) {C=i; R= i +P[i]; }  }   //Find The maximum element in P.  intMaxLen =0; intCenterindex =0;  for(inti =1; I < n1; i++) {    if(P[i] >maxlen) {MaxLen=P[i]; Centerindex=i; }  }  Delete[] P; returnS.substr (Centerindex-1-MaxLen)/2, MaxLen);}

"Result 2"

Time is O (n), 12ms, ranked first

For the hair mid-range problem is so difficult! (? •?_•?)? ┻━┻

Afternoon analysis.

OJ Practice 44--t5 Longest palindormic Substring